The novel role and underlying mechanism of Wnt5a in regulating cellular cholesterol accumulation

摘要

Cholesterol accumulation is a critical step during the development and progression of atherosclerosis. Recently, Wnt5a expression has been found to be markedly upregulated in both murine and human atherosclerotic lesions. However, the effect and mechanism of Wnt5a in atherosclerosis is poorly understood. In the present study, we investigated the effects and potential mechanisms of Wnt5a on cholesterol accumulation during atherosclerosis. We used RAW264.7 and vascular smooth muscle cells (VSMC) treated with oxidized low-density lipoprotein (oxLDL) as lipid-loaded cell models. We found that expression of Wnt5a protein was increased in a concentration (25, 50, 75 and 100 μg/mL)- and time (24, 48 and 72 h)-dependent manner by oxLDL treatment. To explore the underlying mechanism, we used Wnt5a short interference (si) RNA to knockdown Wnt5a expression in both RAW264.7 cells and VSMC, or applied recombinant Wnt5a (rWnt5a) to stimulate Wnt5a signalling. After Wnt5a knockdown, total cholesterol (TC) and free cholesterol (FC) content in both cell types increased significantly (P < 0.05) upon exposure to oxLDL. Conversely, the TC and FC content decreased markedly (P < 0.05) after treatment of cells with rWnt5a. More importantly, both protein and mRNA expression of Caveolin-1 and ATP-binding cassette transporter A1 (ABCA1) was significantly reduced after exposure of wnt5a siRNA-treated cells to oxLDL, whereas rWnt5a treatment of cells resulted in increased Caveolin-1 and ABCA1 protein expression after exposure of cells to oxLDL. Together, these findings demonstrate, for the first time, that Wnt5a reduces the accumulation of cholesterol in lipid-loaded cells by regulating the mRNA expression of Caveolin-1 and ABCA1, which are involved in reverse cholesterol transport. This may present a novel mechanism of Wnt5a-mediated cholesterol transportation in macrophages and VSMC. Therefore, targeting the Wnt5a signalling pathway may have clinical implications in atherosclerosis.